The neuron metal oxide semiconductor field effect transistor (neuron MOSFET) is a device which is relatively new to the integrated circuit community. The neuron MOSFET is formed over a substrate material. A source region, drain region, and a channel region are formed within the substrate material. A floating gate is formed overlying the channel region and separated from the channel region by a gate dielectric. A plurality of control gates is formed overlying the floating gate. Each of the plurality of control gates is formed laterally adjacent each other.
The neuron MOSFET operates differently from both single- control-gate MOSFETs and conventional memory cells. In a neuron MOSFET, no tunneling or hot carrier injection (HCI) is used to generate logic signals. The neuron MOSFET functions by using capacitive coupling. Each of the plurality of control gates is capacitively coupled to the floating gate. The floating gate has the ability to affect the conductivity of the channel region.
Assume, for example, that there are N control gates where N is a positive integer. A control gate is "off" if it is biased to a ground potential, and a control gate is "on" if it is biased at a high potential. The neuron MOSFET is designed so that the transistor is on (i.e. the channel is inverted) if M control gates are "on", where M is less than or equal to N but greater than one. Therefore, the neuron MOSFET operates much like a biological neuron and is more intelligent than a single-control-gate MOSFET.
A disadvantage of the neuron MOSFET is that a large surface area is required to form N control gates laterally adjacent each other. A more compact neuron transistor is required.